The present disclosure relates to a position information detection device applicable to a battery-driven terminal such as, for example, a mobile phone, and more particularly to a position information detection device, a communication apparatus, and a communication system, performing hybrid positioning by combining GPS position information and other position information.
Since 2002, a mobile phone service of a 3G method called the third generation has been in use in Japan. Low-volume packet services such as voice or mail messages were the main application at first. Thereafter, by introducing HSDPA (High Speed Downlink Access) which improves a packet communication rate in a downlink from a base station to a terminal, or the like, downloading of larger-sized packets such as downloading of music files or use (watching) of a moving image sharing service such as YouTube (registered trademark), has been performed.
In addition, along with the increase in capacity of downloaded packets, the wireless network side has also enlarged, and, for example, in the 3GPP system, a HAPA+ service which realizes a maximum of 21 Mbps has started, and, in the IEEE system, a Mobile WiMAX service to realize a maximum of 40 Mbps has started. Further, in the 3GPP system, an LTE (Long Term Evolution) service which uses OFDMA (Orthogonal Frequency Division Multiple Access) in the downlink in a manner similar to the Mobile WiMAX (Worldwide Interoperability for Microwave Access), is scheduled to start in the latter half of the year 2010, and a 4G (LTE-Advanced) service is also scheduled to start around the year 2015. From the start of the services, it is expected that a maximum of 1 Gbps will be realized in semifixed circumstances, and a maximum of 100 Mbps will be realized even in movement circumstances.
In addition, with the variation such as an increase in use of downloading of large-volume data, there has been increasing use of high performance wireless communication terminals called “smart phones” which mainly perform packet communication. In addition, when telecommunications carriers and service providers using the Internet provide further user-oriented services to users in mobile circumstances, position information is becoming increasingly more important information. Under such circumstances, most smart phones have a GPS (Global Positioning System) receiver for detecting position information mounted therein. For example, there has been proposed a wireless communication system in which a base station provides position information of a high accuracy estimation position to a mobile terminal of which a GPS signal is not able to be captured (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-298484). The mobile terminal can operate an application or the like which provides information depending on a current position, based on the high accuracy position information provided from the base station.
The GPS receiver can obtain position information with relatively high accuracy of several meters to several tens of meters in circumstances where signals are able to be received from a GPS satellite. However, a portable terminal which is driven by a battery such as a mobile phone is sensitive to power consumption, and thus there is a problem in that it is difficult to obtain position information by operating the GPS receiver at all times.
For example, there has been proposed a position information measurement system in which a server side receives a current position from a GPS terminal and designates a position where the next position is measured on a movement route of the GPS terminal, the GPS terminal calculates a movement time from the current position to the position where the next position is measured, and the GPS terminal stops the position measurement operation for the movement time (for example, refer to Japanese Unexamined Patent Application Publication No. 2005-337855). Since the GPS terminal stops the movement measurement operation for the calculated movement time, power consumption can be reduced. However, it is difficult to apply the system to a target of which a movement route is not identified.
In addition, since a portable terminal such as a mobile phone is used in a place where a GPS signal is not able to be received such as an indoor location or a basement in many cases, it is preferable to obtain position information with as high accuracy as possible in various circumstances by including position information obtaining functions in addition to the GPS receiver.
For example, there is a technique in which electric measurement information is obtained from a plurality of peripheral public wireless base stations (Wi-Fi access points or 3G base stations), and a current position is measured in real-time based on a balance of the respective reception signal intensities. According to the technique, since the public wireless base station has a wide coverage, it is possible to measure a current position even in a place where a GPS signal is not able to be received such as an indoor location or a basement. However, the base stations are arranged with the units of several kilometers, and thus there is a problem in that the technique has accuracy lower than the GPS.
There is hybrid positioning where positioning is performed by combining position estimations using both position information estimated from Wi-Fi electric measurement information and GPS position information. According to the hybrid positioning, a position can be estimated from Wi-Fi electric measurement information at an indoor location where the GPS is not able to be used, and a position can be obtained from the GPS at a place where Wi-Fi access points are not present in the vicinity.
In addition, there has been proposed a receiver which receives a global positioning system (GPS) signal and a digital broadcasting system (DBS) signal, determines presence states and signal intensities of the GPS signal and the DBS signal via a signal detector of the receiver, selects one positioning mode from a plurality of positioning modes of a signal processing unit of the receiver based on the detected signal presence states and the signal intensities of the signals, and determines a position of the receiver based on the selected positioning mode (for example, refer to Japanese Unexamined Patent Application Publication No. 2007-139772).